The present invention relates to a method of making hose clamps of the so-called open type in which the internal clamping surfaces are devoid of any gaps or steps and to clamps produced by this method.
With the availability of relatively hard and thin plastic hose materials, the step formed at the end of the inner clamping band portion became an ever more likely leakage problem. Additionally, with a tightening device forming a gap under the same, for example, with a so-called xe2x80x9cOetikerxe2x80x9d ear, it became important to bridge the gap underneath the tightening device by the full band width of the inner clamping band portion to avoid a leakage problem. The need for higher tightening forces as well as the desirability of utilizing thin clamping band materials for cost reasons contributed to the need for an internal clamping surface devoid of any gap or step.
The arrangement of a stepless and gap-free internal clamping surface as disclosed in U.S. Pat. No. 4,299,012 to Oetiker provided a practical solution that enjoyed extraordinary commercial success by its use in hundreds of millions of clamps. According to this patent, a tongue-like extension at the end of the inner clamping band portion is adapted to extend through an opening provided in a step-like part of the outer band portion, whereby the step-like part has a height substantially corresponding to the thickness of the clamping band. As explained in my co-pending application Ser. No. 09/689,625, filed on Nov. 13, 2000, now U.S. Pat. No. 6,240,603, substantially all tensional forces are absorbed in such clamps in the outer clamping band portion including the area of the step-like part while the overlapped inner clamping band portion is substantially free of any tensional forces but serves to produce the radial clamping forces in the area of overlap. These clamping forces are produced by a reduction in the diametric dimension of the clamp by the tightening of the outer clamping band portion by means of the tightening device. Thus, within the area of overlap between the outer band portion and the tongue-like extension, the direct clamping action on the surface of the object to be tightened is produced in clamps of the type described in the prior U.S. Pat. No. 4,299,012 by the tongue-like extension alone. It is therefore desirable, on the one hand, to make the tongue-like extension as wide as possible in the transverse direction of the clamping band. On the other hand, to be able to absorb high tensional forces, it is desirable to make the lateral band portions in the step-like part delimiting the opening for the tongue-like extension on both sides thereof as wide as possible. A compromise to accommodate these contradictory requirements thus places some limitations on a designer""s freedom in the design of such a clamp, not only as regards physical dimensions in the clamping band, but also as regards clamping band material. A different approach utilizing a tongue-like extension adapted to engage in the opening formed by a fork-like configuration was disclosed in U.S. Pat. No. 4,237,584 to Oetiker. The concept for a stepless arrangement with a fork-like configuration was then adopted in U.S. Pat. No. 4,750,242 to Calmettes et al. in which a U-shaped configuration at the end of the inner clamping band portion is adapted to engage with a so-called boss of a shape complementary to the U-shaped configuration. However, the clamp as disclosed in this last-mentioned patent involves a potential leakage problem. Apart from the fact that the clamp according to this last-mentioned patent is a fixed-size clamp and provides no suggestion of how the arrangement thereof can be used in a clamp with a tolerance range in the diametric dimension, there is no indication in this patent on how to optimize the length of the blank necessary for a clamp embodying the disclosed arrangement.
Accordingly, it is a primary object of the present invention to provide a method for making open-type clamps which avoids the aforementioned shortcomings and drawbacks and permits a problem-free manufacture of open hose clamps, especially clamps that include a fork-like female profile at the end of the inner clamping band portion adapted to engage with a deep-drawn channel forming a male profile in the outer clamping band portion, whereby the male profile has an external shape in width and depth complementary to the opening in said female profile. The clamp made according to the manufacturing method of the present invention obviates the potential leakage problem of the prior art U.S. Pat. No. 4,750,242 by causing the lateral band parts remaining on both sides of the channel-shaped depression or indentation to merge with the bottom surface of the depression or indentation. The bottom surface of the depression or indentation is thereby at the same radial distance as the internal clamping surfaces of the entire clamp including also the inner clamping surfaces of the inner clamping band portion and of the remainder of the clamping ring and thereby assures a leakage-free arrangement.
However, the present invention is not limited in its application to clamps of the type illustrated in U.S. Pat. No. 4,750,242. Instead, the method of this invention involving a deep-drawn channel configuration can also be applied successfully in the manufacture of clamps of the type disclosed in the prior U.S. Pat. No. 4,299,012 and 4,237,584 with the surprising result that the aforementioned compromise problem can be dealt with more realistically by avoiding the opening in the step-like portion for the tongue-like extension.
Additionally, the present invention provides a disclosure as to the requirements of a clamp of the types mentioned above capable of producing stepless and gap-free clamping forces of the clamp over its entire tolerance range and additionally sets forth the parameters for the particular arrangement of the various parts in the clamping band to optimize clamping band requirements insofar as length of the blank is concerned.